Isotopic signature of anthropogenic sources of groundwater contamination with sulfate and its application to groundwater in a heavily urbanized and industrialized area (Upper Silesia, Poland)

Abstract

Isotopic signatures of anthropogenic sulfate sources within the Upper Silesian urban area (southern Poland) were investigated to increase the reliability of the origin assessment of groundwater contaminants. To analyze δ34S and δ18O in sulfate, 64 samples were collected, representing several sulfate sources: synthetic and organic fertilizers, raw and treated wastewater, mine water, leachate from landfills, mine heaps, and industrial waste dumps. Additionally, 10 surface water samples were taken from contaminated rivers regarded as potential groundwater pollution sources. Results of δ34S and δ18O in sulfate derived from anthropogenic sources were compared with literature data, which indicated significant discrepancies for some contamination sources. The results were applied to assess SO42- origin in groundwater samples from the Gliwice aquifer. Apart from the δ34S and δ18O data, the study included measurements of major ions, inorganic nitrogen forms, trichloroethene and tetrachloroethene in groundwater. Isotopic analyses of river water samples confirmed the impact of urbanized and industrialized areas on surface water pollution and possible influence on groundwater contamination. The values of δ34S and δ18O similar to wastewater were reported for most groundwater samples from the Gliwice carbonate aquifer. Groundwater contamination was also manifested by higher values of electrical conductivity and concentrations of chloride, sodium, trichloroethene and tetrachloroethene. The comparison of recent isotopic data on SO42- sources with literature values clearly shows that it is very important to investigate local potential contamination sources to increase their reliability in determining the source of groundwater or river water pollution.